Dog aggression is defined by us as the intentional desire or attempt to do harm to a person or animal. If your dog has bitten and done harm to a person or animal, we consider that aggression. If your dog lunges at another dog, particularly when walking on leash, we consider that reactivity. Reactive dogs often get on scuffles but rarely bite and very rarely do harm. Reactive dogs are not dangerous to people or animals. If consider you dog dangerous to people or animals, it is prudent to consider him aggressive until proven otherwise.